The recovery of ammonium (NH ₄ ⁺) from model (NH ₄) ₂SO ₄ solutions as well as from sludge liquor of a communal waste water treatment plant was studied on the laboratory scale using the ion exchanger loop stripping process (ILS). The ILS process combines ion exchange and air stripping in a hybrid process and works with fixed bed columns containing natural zeolite (mainly clinoptilolite), which is alternately loaded and regenerated. The sodium hydroxide (NaOH) regeneration fluid is simultaneously air stripped. Ammonium is recovered in a subsequent acid scrubber as concentrated ammonium sulfate solution, which is a suitable reducing agent for industrial NOx recovery. Lab scale experiments with four loading and regeneration cycles demonstrate the technical feasibility of the process. The ammonium equilibrium increased after the first loading and regeneration cycles and ammonium uptake reached concentrations of 3 to 4 mg NH ₄ ⁺ L ⁻¹ over four consecutive cycles. NaOH regeneration at pH values >11.5 recovered nearly the total amount of previously adsorbed ammonium. The stripped amount of NH ₄ ⁺ increased over the investigated cycles and in the final regeneration sequence approximately the whole amount of desorbed ammonium was simultaneously stripped. Ammonium exchange and recovery characteristics did not significantly change when real sludge liquor samples were used.